Waste glass powder, as a kind of solid waste with high content of SiO2, can effectively prevent the strength retrogression of oil well cement stone at high temperature, thereby improving the long-term sealing integrity of cement sheath in deep and ultra-deep wells. The effect of waste glass powder on compressive strength and microstructure of cement stone at 150 ℃， 21 MPa was studied in this paper. The results show that the 180 d compressive strength of neat cement stone is 8.57 MPa, which is 76.04% lower than 1 d compressive strength. The incorporation of waste glass powder improves the long-term stability of cement stone compressive strength. When 40% (mass fraction) cement is replaced by waste glass powder with a particle size of 45 μm, the 180 d compressive strength of cement stone is 31.85 MPa, which is only 3.95% lower than 1 d compressive strength. In addition, the 180 d permeability of cement stone is 1.28×10-2 mD, which is 16.88% lower than 1 d permeability. The incorporation of waste glass powder changes the phase composition of cement stone. The neat cement stone is composed of portlandite and hillebrandite. The cement stone incorporating 40% waste glass powder with a particle size of 45 μm is made up of xonotlite and tobermorite. The grain size of xonotlite and tobermorite in cement stone is stable after incorporating 40% waste glass powder with a particle size of 45 μm. More large pores are produced in neat cement stone with the increase of curing age, while the structure in cement stone incorporating 40% waste glass powder with a particle size of 45 μm is denser, and gel pores are dominated within 180 d.